The present invention relates to an electrostatic chuck having a bonded structure formed by bonding a ceramic electrostatic chuck member and a metal member, and to a method of manufacturing thereof.
As shown in FIG. 2, an electrostatic chuck 25 having a bonded structure contains an electrostatic chuck member 10, a metal member 12 as a base material and a bonding layer 14. And, after a silicon wafer 16 is held (chucked) on the electrostatic chuck member 10 by electrostatic attraction, treatments such as CVD (chemical vapor deposition), sputtering, etching and the like are performed on a surface of the silicon wafer 16 within a system, for example, a CVD system, a sputtering system, an etcher and the like as it is. Further, an electrostatic chuck electrode 18 is embedded in the electrostatic chuck member 10 so that the electrostatic chuck member 10 is charged by applying a voltage from a terminal 20 thereto and the silicon wafer 16 is held with the chuck member by virtue of the resulting electrostatic attraction.
In the electrostatic chuck 25 having bonded structure comprising an electrostatic chuck member and a metal member as described above, when treatments such as CVD, sputtering, etching and the like are performed, which treatments use a plasma reaction, it becomes difficult to control film formation on the silicon wafer because temperature is increased in the silicon wafer due to heat input from the plasma. As a measure to solve the problem, there have been employed the mechanism for cooling the metal member 12, the method for cooling the electrostatic chuck member 10 and the metal member 12 by introducing Ar gas or N2 gas 22 between the electrostatic chuck 10 and silicon wafer 16, or the like. In addition, when the treatments such as CVD, sputtering, etching and the like are performed, which treatments use a plasma reaction, the electrostatic chuck member 10, the metal member 12 and the bonding layer 14 are exposed to a chemically severe atmosphere.
In an electrostatic chuck, there have conventionally been known, as a method of fixing an electrostatic member to a metal member, a method of using a mechanical clamp structure with clamps and bolts, a method of using an organic adhesive or glass as a bonding layer, and the like. When a bonding layer is used, because the bonded structure for an electrostatic chuck is exposed to a chemically severe atmosphere as described above, the bonding layer is required to have good heat conductivity, airtightness, corrosion resistance, and further flatness of the electrostatic chuck member after being bonded, as well as high bonding strength.
In recent years, although ceramic electrostatic chuck members have been widely used, their low mechanical toughness makes it difficult to fix them by mechanical methods such as the use of the mechanical clamp structure and the like. In the case where a general organic adhesive was used, there was a problem that strain and cracks were caused in the surface of the ceramic electrostatic chuck member during use in a wide temperature range, and in the case where glass was used, there was a problem that deformation of a metal member was generated because a high temperature was required for bonding.
In order to solve these problems, JP-A-4-287344 has proposed a bonded structure using a silicone resin in a paste form as a bonding layer, and JP-A-3-3249 has proposed a bonded structure using indium as a bonding layer.
However, in the case where a ceramic electrostatic chuck member and a metal member are bonded using a silicone resin in a paste form or indium as a bonding layer, if bonding pressure is low, a defect will be caused in the bonding, resulting in some problems in reliability of bonding strength and airtightness. On the other hand, if bonding pressure is high, there was caused a problem of making the bonding material bleed out from the joint surface. Moreover, there was such a problem that the flatness of the electrostatic chuck member was deteriorated after bonding due to a difference in thermal expansion between the electrostatic chuck member and the metal member.